﻿118 Dr. W. H. Eccles on the Effect of Electrical 



devoid of hysteresis. This might be interpreted in the same 

 manner as is, usually, the effect of mechanical vibration on 

 iron undergoing varying magnetic forces — the intermolecular 

 bonds that hold the magnetic molecules in their instantaneous 

 configuration are loosened for a moment so that the resultant 

 field can have full play in rearranging the molecular group- 

 ings. Looking further into the matter, however, on this 

 view that hysteresis is temporarily annulled, it is evident that 

 on the ascending loop of the cyclic curve the external applied 

 field is permitted to do work when the magnetic shaking 

 occurs. On the other hand, similar alterations of intensity 

 of magnetization occur when the applied field is zero ; and, 

 in addition, on the descending loop of the cyclic curve there 

 are alterations in intensity opposite in sense to the applied 

 field. It seems clear, then, that there must exist in the 

 magnetized material intrinsic forces that tend to drag the 

 substance into that presumably more stable magnetic state 

 defined by the u normal curve of magnetization " before 

 mentioned. Thus this view that hysteresis is annulled, taken 

 with the experimental facts of this paper, implies that the 

 store of intrinsic energy of magnetization may possibly be 

 allowed to run down through and during the action of the 

 oscillations. In other words, the action of the oscillations 

 may be analogous to the pulling of a trigger. These con- 

 siderations threaten to lead us into the often discussed question 

 of the intrinsic energy of a magnetized material having 

 hysteresis. In the present case there is, besides, the difficulty 

 arising from the fact that different layers of the wire used 

 are doubtless differently affected. Notwithstanding, it is 

 perhaps worth while attempting to answer the question : Is 

 the alteration of stored magnetic energy greater than the 

 initial energy of the oscillations producing the alteration ? 



The latest word on the subject of the intrinsic energy of 

 magnetized iron is contained in a paper by Larmor*. 

 There the expression 27rjl 2 ir, where I is the intensity of 

 magnetization and dr an element of volume, is deduced for 

 the part of the energy we are here concerned with. Taking 

 the observations recorded in this paper for that point of the 

 •200 ampere cycle where the field is zero, the wastage of 

 the intrinsic energy instigated by a spark is, if it be legitimate 

 to apply here this formula, 3600 ergs. Now the initial energy 

 of the oscillations, which exists as the electrostatic energy of 

 the charge on the oscillation-coil just before the spark-gap 

 breaks down, is about 5700 ergs. These figures are too close 

 to enable a decisive conclusion to be reached ; that is, to say 



* Boy. Soc. Proc. Ixxi. p. 229, Feb. 1903. 



